Anchorage for partial denture and method of making same



Dec. 3, 1968 c. N. SKINNER 3,413,722

ANL'HSEGI FOR PARTIAL DENTURE AND METHOD OF MAKING SAME Filed Aug. l, 1966 {44m/VM MA/6 INVENTOR.

nited States Patent O "ce 3,413,722 ANCHRAGE FR PARTIAL DENTURE AND METHD GF MAKING SAME Clawson N. Skinner, 2108 El Rey Drive, Whittier, Calif. 90606 Filed Aug. 1, 1966, Ser. No. 569,372 4 Claims. (Cl. 32--5) This invention relates to partial dentures and more particularly to an improved anchorage for a partial denture so constructed and arranged as to permit limited vertical pivotal movement during mastication without risk of excessive strain on the denture anchorage.

Partial dentures have been proposed and used heretofore equipped with separable connectors to an anchorage rigid with adjacent dental structure. Typically, such separable connectors are located at one end of the partial denture and include a rigid male member integral with the anchorage and having a telescopic t with a generally U-shaped female component embedded in the partial denture and held assembled thereto by a removable pin passing transversely through the connector parts. By this arrangement it is a relatively simple matter to install and remove the denture. One of the shortcomings of such prior constructions is the lack of any provision for limited vertical movement of the partial denture relative to the fixed anchorage. During mastication the partial denture is subjected to considerable stress causing the underlying tissue and bony structure to give with the result that excessive strain is placed on the anchorage apt to cause warping or premature failure of the anchorage tooth structure.

To avoid these problems and to provide a precision separable connector between a partial denture and its anchorage, there is provided by the present invention a novel structure and method of fabricating the same utilizing lost wax techniques with which dentists are fully familiar and at the same time permitting each customized denture appliance to have limited vertical pivotal movement toward the underlying supporting alveolar ridge. These objectives are accomplished by providing precision plastic patterns of the hinge components including an elongated male component adapted to have one end attached to the wax impression for the anchorage and a female component adapted to he embedded in the base of the partial denture. These components are then used as patterns in a lost wax operation to form an investment mold wherein the investment material shrinks exactly to the same degree in all parts of the cavities during processing. Thereafter, the wax and fusible plastic patterns are removed from the investment leaving cavities useful in forming actual castings of the anchorage and of the companion part of the connector to be embedded in the denture. During the assembly of these castings to the denture, a wedge-shaped plastic or metal component is added to the upper side of the male connector member and used in forming a flask mold for the base of the partial denture. After this base has been molded, the parts are separated and the wedge member is removed leaving a shallow wedge-shaped cavity in the denture base directly overlying the male connector member and into which the male connector is movable when higher pressures are applied to the denture.

Accordingly, it is a primary object of the present invention to provide an improved partial denture assembly having a separable connector so constructed as to permit limited vertical pivotal movement of the denture relative to the anchorage and to provide a simple technique usable by the dentist in fabricating his own customized partial denture assemblies to meet individual patient requirements.

Another object of the invention is the provision of a simple lost wax procedure for fabricating separable connectors for partial dentures featuring limited vertical piv- Patented Dec. 3, 1968 otal movement and suitable for use by the ordinary dentist without need for special training.

Another object of the invention is the provision of an improved separable connector and anchorage assembly for partial dentures incorporating provision for limited pivotal movement of the denture without imposing strain on the anchorage structure.

These and other more specific objects will appear upon reading the following specification and claims and upon considering in connection therewith the attached drawings to which they relate.

Referring now to the drawings in which a preferred embodiment of the invention is illustrated.

FIGURE l is a general diagrammatic View of an investment mold showing the fusible parts of the invention connector in readiness for investment;

FIGURE 2 is an exploded perspective view of the pattern components for the connector and showing the male component affixed to one end of the wax impression for the anchorage unit;

FIGURE 3 is a cross-sectional view showing the assembled cast connectors assembled with a wedge-shaped component in the wax uncured plastic base of the denture within a ask mold;

FGURE 4 is an exploded view of the finished cured partial denture after removal from the flask mold and showing the wedge-shaped member removed;

FIGURE 5 is a fragmentary view of the connector end of the partial denture with the male member pivoted so as to rest against the upper side of the cavity formed by the wedge-shaped member; and

FIGURE 6 is a fragmentary view on an enlarged scale taken generally along line 6-6 on FIGURE 5.

Referring initially more particularly to FIGURE 2, there is shown the pattern components useful in forming cavities in investment material in accordance with the known principles of the lost wax casting process and from which metal castings can be made for subsequent installation in the patients mouth. These components include a generally U-shaped pattern 10, a male pattern 11, and a hinge pin pattern 12. As herein illustrated, the unshown mounting shank for pattern element 11 is embedded within the adjacent end of a wax impression 13 to be used in casting the fixed anchorage for the partial denture. It will be understood that pattern components 10, 11 and 12 are precision formed from fusible plastic material. This assures accurate formation of the cavity in investment material and the subsequent accurate casting of metal parts duplicating pattern elements 11, 12. lt is pointed out that pattern 10 has an elongated slot 1S extending lengthwise thereof corresponding closely in shape and size to the tang portion of male member 11 and that it opens through both the upper and lower faces of pattern 10. Boss 16 formed on one side face of pattern 1f! is threaded to mate with threaded portion 17 of hinge pin 12, the far end of this pin extending through an aligned opening in the far side of pattern 10. In addition, pattern 10 is provided with one or more anchorage loops 1S for use to interlock the connector more firmly to the base of the partial denture, all as will become evident below.

Additionally, it is pointed out that the wax impression 13 for use in anchoring the partial denture to the patients original teeth may take any of many configurations, the one herein shown being typical and designed to lie along the inner face side of the lower teeth and having enlargements at its opposite ends adapted to embrace or crown a pair of anchor teeth.

After male member 11 has been secured to one end of wax impression 13 in position to project over the gum area of the edentulous area, the dentist or technician is ready to proceed with the preparation of the common investment for subassemblies 11 and 13 on the one hand and 10 and 12 on the other hand. These are placed in a common block of investment material of any suitable known character 20 and in the general manner illustrated in FIGURE l. The investment material is provided with suitable channels 21 terminating at the pattern elements, the outer ends of each opening outwardly through the exterior of the investment to provide passages from which the fusible pattern material escapes and through which the molten casting metal is later introduced to ll the cavity.

The investment having been completed, the fusible material is removed by known technique following which the completely cleaned cavities are lled with suitable casting metal, as gold, following which the investment is broken away from the completed casting.

The technician next proceeds to prepare the partial denture proper using an impression of the area to be occupied by the denture made by the dentist. This technique is well known to those skilled in this art and need not be detailed here beyond outlining the final phases of the operation which are illustrated in FIGURE 5. It will be understood that a two-part flask mold 22 is prepared having an interior surface 23 conforming to the portions of the patients alveolar ridge to be contacted by the adjacent surface of the denture ibase 24 as well as other surfaces shaped suitably to mold the exposed surfaces of the base. Artificial teeth vare accurately positioned and supported in cavities of the mating part of the flask mold following which the base-forming portion of the cavity is packed with uncured plastic such as acrylic. This packing operation is performed by hand while the casting components of the hinging connector are held firmly and laccurately in place therein. In the interest of simplicity the casting components are identified by the same numerals used to identify the corresponding pattern parts but are distinguished therefrom by the addition of a prime. In this connection it will be understood that, as initially cast, the vertical thickness of male member 11 corresponds with the vertical height of the sidewalls of female member 10. In order that the limited vertical pivotal movement desired in the finished assembly between the male and female members may occur between the upper and lower surfaces of the female member, it is preferable to remove a wedge-shaped portion from the upper surface of member 11' rather than to form a wedge-shaped cavity in the denture base and directly overlying the male member. Hence the technician files or grinds away a wedge-shaped portion from the top of the male'member, ,the thicker end of the wedge typically being l to 15 mils in thickness. The metal so removed is then replaced temporarily by a wedge element 27 of polished aluminum, silicone plastic or the like material to which the acrylic will not bond and having its upper surface lying flush with the upper surface of female member as is shown in FIGURE 3. The pointed end of wedge insert 27 abuts the adjacent edge of a crosspiece 28 serving to interconnect the forward ends of the U- shaped female member 10'. As will Ibe apparent, hinge pin 12' holds the connector parts accurately assembled while the cavity is Abeiu'g packed with uncured acrylic.

The assembled mold 22 is processed to cure the acrylic following which the mold is broken away permitting hinge pin 12' to be removed, and permitting male hinge member 11 to be withdrawn so that wedge 27 can be detached. The parts can then be reassembled leaving the space overlying the upper side of male member 11' vacated and available to accommodate limited ver-tical hinging movement about pin 12. Normally, the partial denture occupies the position shown in FIGURE 4 with the lower surface of base 24 supported against the ridge tissues. However, when masticating pressure is applied, the tissues give and the denture base pivots counterclockwise about pin 12' and until the upper side of male member 4 11 seats against surface 27 in the manner shown in FIGURE 5.

Small as this pivotal movement is, it nevertheless is found adequate and highly effective in relieving severe stress which would otherwise be imposed on the anchorage for the partial denture. It is found that patients using the described connection are able to masticate food with comfort and to apply much greater pressure than is otherwise possible-and without overstressing the anchorage structure for the denture. Furthermore, the pressure so applied to the tissues stimulates blood circulation therein and aids in maintaining the same strong and healthy.

Attention is also invited to FIGURE 6 showing connector hinge pin 12' as having an enlarged head the inner end of which is threaded at 17 and the outer portion of which is preferably left Unthreaded but with one or more ats 32 for engagement by tools and useful in assembling the hinge pin. While not shown in FIGURE 6, it will be understood that the denture base is usually made with its outer surface lying flush with the outer end of the pin and with a small encircling cavity for the accommodation of a pin operating tool.

In addition, it is pointed out that boss 16' provides adequate room for threads engageable with the hinge pin and avoids weakening the female casting itself lwith such threads.

While the particular anchorage for partial denture and method of making same herein shown and disclosed in detail is fully capable of attaining the objects and providing the advantages hereinbefore stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as defined in the appended claims.

lI claim:

1. That method of completing and assembling a partial denture for limited pivotal movement toward the alveolar ridge and relative to a fixed anchorage for said denture which method comprises: forming separate accurately cooperating male and female hinging members having a transverse hinge axis and with said male member integral with said xed anchorage, applying a thin wedgeshaped element to the upper side of said male member with the pointededge of the wedge close to said fixed anchorage and the thick end thereof opposite the free end of said male member, embedding the assembled connector components in the base of a partial denture and thereafter removing said wedge-shaped element to leave a low-height cavity to permit the denture to have slight pivotal movement in a vertical plane about said hinge axis and to permit the denture to pivot toward the asspciated alveolar ridge and thereby to avoid excessive tran on the denture `anchorage during mastication of 2. That method of preparing a separable hinging connection between a partial denture and an anchorage therefor adapted to be 4iixedly attached to a patients dental structure and incorporating provision for limited vertical pivotal movement of the partial denture toward the associated alveolar ridge and about a pivot axis extending transversely of said denture and said separable connections which method comprises: embedding the anchor end of a fusible pattern of the male member of a separable hinging connector for a partial denture in a wax pattern of an anchorage for that partial denture, placing the assembly so formed in investment molding material along with a fusible pattern of the mating female member of said hinging connector and heating the same to embed said wax and fusible paterns within said investment material, treating said investment to remove the wax and plastic and thereafter lling the vacated cavities with molten metal, removing the castings from the investment, assembling the connector parts, applying a thin wedgeshaped member along the upper side of the male member and embedding the assembly so formed in the base of a partial denture, and disassembling said hinging connector and removing the Wedge-shaped member to provide room in the partial denture for limited vertical hinging movement of said denture relative to the xed anchorage for the male portion of said connector.

3. A partial denture and anchorage assembly comprising, an anchorage casting adapted to be iXedly secured to a patients dental structure and having an elongated integral male hinge member projecting therefrom and closely overlying an edentulous gum area, a partial denture saddle formed for straddling support on said gum area and having embedded in one end thereof a female hinge member with an elongated opening through the top side thereof coextensive in length and width with said male hinge member and so dimensioned along the top thereof relative to said male member as to provide a wedge shaped cavity to permit slight vertical pivotal movement of said partial denture toward said gum area and relative to said xed anchorage as masticating pressure -is applied to said denture by the user.

4. A partial denture and anchorage assembly as dened in claim 3 characterized in the provision of a hinge pin pivotally connecting said male and female hinge members and having a threaded head end of larger diameter than the main body thereof, and a threaded boss formed on one exterior side of said female hinge member having threads mating -with the threads on said hinge pin.

References Cited UNITED STATES PATENTS 4/1942 Skinner 32-5 5/1950 Skinner 32-5 XR 

3. A PARTIAL DENTURE AND ANCHORAGE ASSEMBLY COMPRISING, AN ANCHORAGE CASTING ADAPTED TO BE FIXEDLY SECURED TO A PATIENT''S DENTAL STRUCTURE AND HAVING AN ELONGATED INTEGRAL MALE HINGE MEMBER PROJECTING THEREFROM AND CLOSELY OVERLYING AN EDENTULOUS GUM AREA, A PARTIAL DENTURE SADDLE FORMED FOR STRADDING SUPPORT ON SAID GUM AREA AND HAVING EMBEDDED IN ONE ONE THEREOF A FEMALE HINGE MEMBER WITH AN ELONGATED OPENING THROUGH THE TOP SIDE THEREOF COAEXTENSIVE IN LENGTH AND WIDTH WITH SAID MALE HINGE MEMBER AND SO DIMENSIONED ALONG THE TOP THEREOF RELATIVE TO SAID MALE MEMBER AS TO PROVIDE A WEDGE SHAPED CAVITY TO SAID MALE MEMBER AS TO PROVIDE A MENT OF SAID PARTIAL DENTURE TOWARDL SAID GUM AREA AND RELATIVE TO SAID FIXED ANCHORAGE AS MASTICATING PRESSURE IS APPLIED TO SAID DENTURE BY THE USER. 